A technique called as COB (CHIP ON BOARD) has attracted attention in recent years, as a way of mounting electronic components on a circuit board, in which electronic components are mounted onto electrodes on a circuit board in a state of the electronic components faced downward. The COB technique will be described with reference to the drawings.
FIG. 10A is a flow chart of the conventional COB method. Based on this figure, the description is made. Referring first to FIG. 10B, according to the conventional COB method, an electronic component b is first arranged and bonded to a circuit board d. Electrode parts c as shown in FIG. 10B are provided on the circuit board d for the electric connection to the electronic component b. The circuit board d is held at a stage a in FIG. 10B. Meanwhile, electrode parts of the electronic component b have bumps e to be bonded with the electrode parts c of the circuit board d. Each bump e is coated with a silver paste or the like for the bonding. The electronic component b is transferred while being sucked by a nozzle f, and positioned at an arrangement position on the board d. After the electronic component b is arranged on the board d, the silver paste is fused by heat thereby to bond the electronic component. Thereafter, a sealant is applied in the periphery of the electronic component b as indicated in FIG. 10C. The sealant i is applied by a dispenser h along a higher position side of the electronic component b after the circuit board d is held slantwise with the use of, for instance, an inclination stage g shown in FIG. 10C. In this manner, the applied sealant i is allowed to flow to a lower portion of the electronic component b along the inclination of the circuit board d. The sealant i is set with heat to complete the bonding. Reference symbol j in FIG. 10C indicates a positioning base for positioning the circuit board d.
The conventional method as above finds difficulty in flowing the sealant i to the lower portion of the electronic component b, because a gap between a lower face of the electronic component b and the circuit board d is as narrow as several tens .mu.m, and moreover the sealant i is highly viscous. A feed time for the flow of sealant i is consequently apt to be lengthy, in other words, production time is lengthened thereby lowering production efficiency. Besides, the sealant i fed to the gap tends to be insufficient in feed amount, resulting in the formation of air bubbles which are to be enclosed. When the air bubbles are present between the component b and the circuit board d, and the periphery of the electronic component b is sealed to tightly close the gap between them, an expansion/shrinkage of the air in the bubbles will occur due to change of the surrounding temperature. A pressure increase or decrease due to the expansion/shrinkage of air bubbles sometimes invites breaks of the electronic component b or the humidity in the air bubbles causes corrosion of the electrode or the like, thus leading to mounting faults.
The present invention is devised to solve the aforementioned issues, and has for its object to provide a method for mounting an electronic component by applying a sealant beforehand at an arrangement position of the component on an object where the electronic component is to be mounted thereby to positively apply the sealant under the electronic component, so that the electronic component can be sealed quickly and sufficiently with the occurence of breaks, corrosion or the like mounting failures being reduced, thereby improving production efficiency, and an apparatus and a dispenser used in the method.